1. Field of the Invention
This invention relates to devices relying on magnetic properties and, more particularly, those which in operation rely on magnetic properties to support single wall magnetic domains.
2. Art Background
An integral part of any magnetic bubble device is a layer of a material that has a magnetic anisotropy that is capable of supporting single wall magnetic domains. One general class of such domain supporting materials has a garnet crystal structure. Thus, the interest in magnetic devices has generated a corresponding interest in garnet materials exhibiting the necessary anisotrophy.
Generally, garnet based devices have a growth-induced magnetic anisotropy produced by ions located on the dodecahedral sites of the crystal. This growth-induced component results from the presence of a magnetic rare earth ion, such as samarium, in conjunction with a different, either magnetic or non-magnetic, rare earth ion. (For purposes of this disclosure, yttrium is considered a rare earth ion.)
The growth procedures necessary to produce such garnets are well established and are commercially viable. In using these procedures to obtain an acceptable growth-induced magnetic anisotropy, e.g., an anisotropy greater than approximately 7,000 ergs/cm.sup.3, a substantial percentage of the dodecahedral sites must be filled with the necessary growth-induced anisotropy producing rare earth ions. Thus, once a suitable anisotropy is achieved in a particular crystal--especially in a material supporting small diameter magnetic domains where large growth-induced anisotropies, e.g., greater than 80,000 ergs/cm.sup.3 are required--relatively few dodecahedral sites remain available for substitution. Often it is desirable to increase anisotropy or change the properties of the garnets by further substitution on the dodecahedral sites. Obviously, it is desirable to perform this substitution by well established growth procedures. As discussed in the case of garnet materials, the possibility of significant substitution on the dodecahedral site using established techniques typically is not available. Thus, the opportunity for tailoring of garnet material properties by adjusting the composition of the dodecahedral site is significantly limited.